Which is an example of energy conversion?

• A. Ultrasound
• B. Conduction
• C. Convection
• D. Evaporation

Answer: (A)

Energy conversion means changing energy from one form to another. An ultrasound device does this by using a piezoelectric crystal that converts electrical energy into mechanical energy to produce acoustic waves. This is a direct energy form change: electrical energy becomes mechanical (sound) energy.

Conduction, convection, and evaporation describe ways heat is transferred or a phase change that consumes or releases energy, but they don’t illustrate a device transforming energy from one form to another. Conduction and convection move thermal energy through contact or fluid flow, while evaporation involves energy input to change a liquid to vapor, not a change from electrical to another energy form.